The human brain consists of billions of neurons and these neurons pool together in groups at different scales. On one hand, these neural entities tend to behave as single units and on the other hand show collective macroscopic patterns of activity. The neural units communicate with each other and process information over time. This communication is through small electrical impulses which at the macroscopic scale are measurable as brain waves. The electric field that is produced collectively by macroscopic groups of neurons within the brain can be measured on the surface of the skull via a brain imaging modality called Electroencephalography (EEG). The brain as a neural system has variant connection topology, in which an area might not only be connected to its adjacent neighbors homogeneously but also distant areas can directly transfer brain activity [16]. Timing of these brain activity communications between different neural units bring up overall emerging spatiotemporal patterns. The dynamics of these patterns and formation of neural activities in cortical surface is influenced by the presence of long-range connections between heterogeneous neural units. Brain activity at large-scale is thought to be involved in the information processing and the implementation of cognitive functions of the brain. This research aims to determine how the spatiotemporal pattern formation phenomena in the brain depend on its connection topology. This connection topology consists of homogeneous connections in local cortical areas alongside the couplings between distant functional units as heterogeneous connections. Homogeneous connectivity or synaptic weight distribution representing the large-scale anatomy of cortex is assumed to depend on the Euclidean distance between interacting neural units. Altering characteristics of inhomogeneous pathways as control parameters guide the brain pattern formation through phase transitions at critical points. In this research, linear stability analysis is applied to a macroscopic neural field in a one-dimensional circular and a twodimensional spherical model of the brain in order to find destabilization mechanism and subsequently emerging patterns. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Wide spread consumer adoption of self-driving cars (SDC) is predicated on a level of trust between humans and the autonomous vehicle. Despite advances being made in the technical abilities of SDCs, recent studies indicate that people are negatively predisposed toward utilizing autonomous vehicles. To bridge the gap between consumer skepticism and adoption of SDCs, research is needed to better understand the evolution of trust between humans and growing autonomous technologies. The question of mainstream acceptance and requisite trust is explored through integration of virtual reality SDC simulator, an electroencephalographic (EEG) recorder, and a new approach for real-time trust measurement between passengers and SDCs. An experiment on fifty human subjects was conducted where participants were exposed to scenarios designed to induce positive and negative trust responses. Emotional state was quantified by the EEG beta wave to alpha wave power ratio, and participants self-reported their levels of trust in the SDC after each segment. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Speech perception is a unique audiovisual experience in part because timing of the speech signal is influenced by simultaneous overlapping gestures in coarticulation. Apraxia of speech (AOS) is a motor planning disorder that impairs coarticulation. Imaging studies show that brain regions damaged in AOS are critical to audiovisual speech perception. Although AOS is a motor planning disorder, individuals with AOS may have a disruption to the perceptual system for speech gestures. To evaluate this hypothesis we investigated audiovisual mismatch negativity (MMN) brain responses in adults with damage to Broca’s area (n =5) compared to a healthy age-matched comparison group (n = 5). We utilized the McGurk effect, in which incongruent auditory and visual information alters perception. Participants viewed videos of a speaker articulating the syllable /ba/ (standard) for 80% trials and /ga/ (deviant) for 20% of the trials while the auditory stimulus /ba/ remained consistent throughout. Responses to this McGurk audiovisual condition were compared to an inverse McGurk audiovisual condition in which the visual stimulus remained constant while the auditory stimulus changed, and a visual-only condition without sound to control for evoked activity from changes to the visual stimulus. Incongruent McGurk deviants elicited an MMN over left hemisphere electrodes in the comparison group, while the AOS group exhibited a later, attention-based response, a P300. The AOS group similarly responded to inverse McGurk deviants, which do not require fusion of the percept, with a P300 response, indicating that auditory and visual aspects of the incongruent McGurk deviants were not integrated. In the visual-only control condition, the AOS group showed a left-lateralized MMN, suggesting greater influence of visual processing when confronted with conflicting multisensory information compared to the comparison group. Overall, the comparison group’s responses were indicative of early and automatic audiovisual integration of incongruent McGurk percepts while the responses of the AOS group showed contributions of both attentional and visual processing. The timing of the response in the AOS group was correlated with speech production characteristics of apraxia, as well as performance on taxing motor speech tasks. Results of this study support the hypothesis that AOS is a disorder beyond motor planning, with implications for higher-level linguistic and cognitive systems.

Bonifácio, P.R.C. Estudo da sincronização e dessincronização cortical em EEG associada a movimento de membros inferiores. 84 f. Dissertação (Mestrado) – Escola Politécnica, Universidade de São Paulo, São Paulo, 2006. Quando o ser humano prepara a execução de um movimento conhecido e treinado, é possível identificar as fases desta preparação no sinal eletrencefalográfico (EEG), sobre as faixas de freqüência delta, mu, beta e gama. A preparação do movimento dos membros inferiores pode ser antecipada em milhares de milissegundos e a facilitação descendente no sistema nervoso central pode ser identificada. Este trabalho sistematiza um processo de aquisição para o sinal de preparação motora baseado no EEG, em área associada a membros inferiores, como subsídio à identificação de Sincronização e Dessincronização corticais, nas faixas de freqüência acima de 13Hz, como reflexo da interação funcional de alças córtico-talâmicas, para movimento conhecido e treinado, em tarefa de retardo instruído. Buscou-se comprovar a possibilidade de uso de um número reduzido de cinco canais de EEG para monitorar esta preparação cortical, bem como formalizar a possibilidade de usar o sinal processado nas faixas beta e gama. Foram obtidos resultados coerentes com a literatura, com dessincronização mu e beta com todos os sujeitos e sincronização gama evidenciada em metade dos sujeitos. Como resultado principal ficou evidenciado que: o uso de cinco canais suportando a coleta de EEG apresenta-se cabível e possui uma boa capacidade de discriminação dos fenômenos de ERS/ERD nas faixas de interesse, para o monitoramento da atividade cortical pré-movimento para membros inferiores; que é possível identificar, no paradigma empregado, os períodos de envio de informação para os tratos descendentes, e quais são as condições mínimas para realizar o monitoramento com a preparação ambiental adequada para evitar os distratores mais conhecidos. / The analysis of the electroencephalogram (EEG) enables the identification of a pre-movement activity associated with the execution of a known and pre-trained movement. The main frequency bands to achieve this identification are the delta, mu, beta and gamma. The initiation of the movement of the legs can be anticipated by thousands of milliseconds by a suitable analysis of the EEG. The objective of this work is to develop signal acquisition and signal processing methodologies associated with the scalp EEG during pre-movement trials. The EEG recordings are concentrated over the leg cortical area with the objective of identifying cortical synchronization and desynchronization (ERS/ERD) associated with trained movements. The number of available EEG channels was limited to five and one task was to investigate if this low number of channels would be enough for the purposes of monitoring cortical preparation. The results were consistent with those presented in the literature. In all subjects mu and beta desynchronization were observed and in half (four) of them the gamma band showed synchronization. One conclusion was that the cortical ERS/ERD associated with the lower limbs are recognizable using only five EEG channels. Several aspects of the experimental paradigm and the signal processing were adjusted for optimal results. members, foot, leg.

People with schizophrenia are known to have difficulties with episodic memory (EM). The purpose of this investigation was to examine the relationship between theta-power and: i) behavioural measures of EM performance, ii) event- related potential (ERP) indices of recollection and, iii) measures of schizophrenia symptomatology. In doing so, the aim was to gain a better understanding of the basic neural mechanisms that contribute to successful EM performance, and how these may differ for people with schizophrenia. The present investigation adopted an endophenotypic approach and collected measures of schizotypy from student participants to minimise patient factors that can confound interpretations. Fifty- four participants were asked to complete a reality-monitoring exclusion EM paradigm whilst electroencephalogram (EEG) data were collected. Measures of theta-power and ERPs were time-locked to words presented during the retrieval phase. There was a significant positive correlation between theta-power over Fz between 600-1000ms post-stimulus presentation and estimates of recollection in the imagine condition as well as a significant negative correlation between these measures of theta-power for perceive items and ERP indices of recollection for imagine items. There was also a significant positive correlation between measures of frontal theta-power in the imagine condition and negative schizotypy. The epoch employed means it is likely these measures of theta- power reflect processes contributing to the content-specific retrieval of imagined items, and post-retrieval processes acting in service of differentiating imagined items in EM. Results are discussed in terms of suggestions for interventions and directions for future research.

No description available.

Bonifácio, P.R.C. Estudo da sincronização e dessincronização cortical em EEG associada a movimento de membros inferiores. 84 f. Dissertação (Mestrado) – Escola Politécnica, Universidade de São Paulo, São Paulo, 2006. Quando o ser humano prepara a execução de um movimento conhecido e treinado, é possível identificar as fases desta preparação no sinal eletrencefalográfico (EEG), sobre as faixas de freqüência delta, mu, beta e gama. A preparação do movimento dos membros inferiores pode ser antecipada em milhares de milissegundos e a facilitação descendente no sistema nervoso central pode ser identificada. Este trabalho sistematiza um processo de aquisição para o sinal de preparação motora baseado no EEG, em área associada a membros inferiores, como subsídio à identificação de Sincronização e Dessincronização corticais, nas faixas de freqüência acima de 13Hz, como reflexo da interação funcional de alças córtico-talâmicas, para movimento conhecido e treinado, em tarefa de retardo instruído. Buscou-se comprovar a possibilidade de uso de um número reduzido de cinco canais de EEG para monitorar esta preparação cortical, bem como formalizar a possibilidade de usar o sinal processado nas faixas beta e gama. Foram obtidos resultados coerentes com a literatura, com dessincronização mu e beta com todos os sujeitos e sincronização gama evidenciada em metade dos sujeitos. Como resultado principal ficou evidenciado que: o uso de cinco canais suportando a coleta de EEG apresenta-se cabível e possui uma boa capacidade de discriminação dos fenômenos de ERS/ERD nas faixas de interesse, para o monitoramento da atividade cortical pré-movimento para membros inferiores; que é possível identificar, no paradigma empregado, os períodos de envio de informação para os tratos descendentes, e quais são as condições mínimas para realizar o monitoramento com a preparação ambiental adequada para evitar os distratores mais conhecidos. / The analysis of the electroencephalogram (EEG) enables the identification of a pre-movement activity associated with the execution of a known and pre-trained movement. The main frequency bands to achieve this identification are the delta, mu, beta and gamma. The initiation of the movement of the legs can be anticipated by thousands of milliseconds by a suitable analysis of the EEG. The objective of this work is to develop signal acquisition and signal processing methodologies associated with the scalp EEG during pre-movement trials. The EEG recordings are concentrated over the leg cortical area with the objective of identifying cortical synchronization and desynchronization (ERS/ERD) associated with trained movements. The number of available EEG channels was limited to five and one task was to investigate if this low number of channels would be enough for the purposes of monitoring cortical preparation. The results were consistent with those presented in the literature. In all subjects mu and beta desynchronization were observed and in half (four) of them the gamma band showed synchronization. One conclusion was that the cortical ERS/ERD associated with the lower limbs are recognizable using only five EEG channels. Several aspects of the experimental paradigm and the signal processing were adjusted for optimal results. members, foot, leg.

This thesis reports on several new and innovative instrumentation developments to solve some of the problems of brain activity monitoring, particularly SSVEP (Steady State Visual Evoked Potentials) studies. SSVEP systems generate suitable stimuli and record the resulting brain biopotentials from scalp electrodes. The instrumentation is configured as a 'Neuropsychiatric Workstation', supporting up to 136 scalp electrodes. Operating in the SSVEP mode, the Neuropsychiatric Workstation reported here significantly improves upon the previously reported spatial resolution and accuracy of maps related to the generated stimuli. These maps allows insights to be gained into the cognitive workings of the brain. A significant component of the work reported here covers the development of the multielectrode EEG measurement modules and the associated techniques for minimising interference and cross-talk. The techniques for synchronising recordings from all electrodes with the stimulus, interfacing to a host computer and real-time storage of the very large amounts of data generated to hard disk, are all reported. The SSVEP paradigm uses a sinusoidal-modulated visual stimuli. A novel linearised LED (light emitting diode) head-up display was developed, in addition to more conventional stimuli, such as the alternating checker-board display, all with sinusoidal modulation capability over a range of frequencies. The Neuropsychiatric Workstation described in thesis has been replicated several times and is in regular use at Brain Sciences Institute (BSI) at Swinburne University of Technology, and other collaborative research institutes.

As mobile phone connections approach two billion worldwide and become steadily more available and affordable, demands for scientific studies on the effect of such EMFs on human functioning similarly increase. The current thesis systematically investigated the effects of acute mobile phone exposure on human brain activity and performance using an in-vivo approach. The research question comprised the following parts: First, is human neural function sensitive to acute mobile phone exposure? Second, if so, what processes are affected? Third, if so, do these neural changes affect gross measures of performance or behaviour? A review of the previous literature found that there was some, but not conclusive evidence that mobile phone exposure affects neural function and some aspects of human performance, and that the studies in question required replication with reliable and realistic dosimetry, double-blinding and additional technical tests to ensure that the experimental set-up was free of artefact contamination. A pilot study was conducted to provide an indication of possible future results, assist in the formation of hypotheses for the main study, and highlight what technical issues required attention before the main study could begin. Results of the pilot study indicated that EMFs emitted by GSM900 mobile phones may alter human brain activity during an auditory task, particularly in proximity to the phone. Both early sensory and later more cognitive ERP components were significantly altered during active compared to sham exposure. Results also suggested that mobile phone exposure may hinder human performance, with longer RTs during the active exposure relative to the sham exposure. However, due to the small sample size of the pilot investigation and questions remaining as to possible technical limitations of the study, these results were treated with caution and used primarily in the formation of future hypotheses for the larger experimental study. Subsequent technical tests provided improvement and validation of the experimental set-up and exposure delivery system, and ensured that future research would be free from such technical limitations. These tests included the characterisation of spectral emissions by the test phone; ensuring that EMFs emitted by the test phones would not interfere with, nor distort, data from the response pad or that processed by the electrode leads; determining whether electrode leads cause an increase or decrease in SAR; and examining the issue of experimenter interference. These tests enabled the conclusion that a positive finding from the large experimental trial would be due to the active exposure of the mobile phone, or in the case of a null finding, would not be due to insufficient or unreliable exposure. Applying the knowledge gained from these technical tests, the main study aimed to provide results of a definitive nature by employing a sample size of 120 sufficient statistical power to detect relatively subtle effects, and a stringent methodological design to account for past limitations. The main study also increased the scope of investigation beyond that achieved in previous research by including endpoints related to sensory processing (auditory and visual tasks), higher cognitive processing (cardsorting task), performance (reaction time and accuracy) and cortical activation (EEG alpha power). To increase this scope even further, within these tasks, the study used data from each scalp electrode and offered insights into the effect of laterality (ipsi- versus contralateral in relation to the exposure source), psychological arousal, perception of transmission, and between-subject factors such as age, gender, previous mobile phone use and hemisphere exposed (right versus left hemisphere exposure). The results of the main study suggested that acute exposure to GSM900 mobile phone significantly reduced levels of psychological arousal, particularly in relation to selfratings of Energy. Results also indicated that only minutes of active exposure can lead to enhanced alpha EEG activity during active exposure relative to sham exposure. Interestingly, this effect was found to be transient, decreasing below sham levels after ten minutes of active exposure and up until ten minutes after exposure cessation. These exposure-induced changes in EEG alpha power were here interpreted as representing an overall reduction in integrative brain function, possibly caused by the physiological response to neural interference or altered synaptic transmission. Acute exposure did not alter human brain activity in the form of the early sensory or later cognitive ERP responses during an auditory or visual task, or EEG synchronisation during a higher cognitive task. The findings also suggested that resultant behaviour, as indexed by RT and accuracy, is unaffected by exposure. Conversely, exploration into specific groups within the sample resulted in some interesting interactions, which raised the possibility that active mobile phone exposure may affect individuals differently as a function of age, gender and which hemisphere is exposed. Specifically, the auditory processing of older individuals was particularly vulnerable to the detrimental effects of mobile phone exposure compared to their younger counterparts. Results of the visual task suggested that the performance of females may also be particularly vulnerable to the detrimental effects of active exposure, compared to males. Overall, the present study has confirmed that there are mobile phone-related bioeffects at the low levels that mobile phones are permitted to operate at. Although various effects have been observed, there is no indication from the present results that cumulative effects or any health consequences exist as this was not the focus of the research. It is argued that future investigation into mobile phone-related bioeffects should apply more sophisticated methodologies to the investigation of acute exposure on EEG alpha power and higher cognitive functioning, as well as larger sample sizes and fewer carefully planned comparisons in order to detect small effects. Further investigation into exposure-induced effects on different groups according to age, gender and which hemisphere is exposed should also be a priority.

No description available.